manganese star

A B star, with a surface temperature of 10,000
to 15,000 K whose spectrum shows an unusually high ratio of manganese to iron. This and other chemical anomalies
are due to the physical separation of different kinds of ions in the stellar
atmosphere. Manganese stars rotate slowly, as Ap
stars do, but lack their strong magnetic fields. In their spectra, temperature,
and other properties, they are intermediate between Ap stars and Am
stars.

A mercury-manganese star is a type of manganese star the spectrum
of which has a prominent line at 3984 Å due absorption by ionized mercury. A bright example is Alpheratz (Alpha Andromedae).